actually you are wrong bro.....your ALTERNATOR(s) are there to supply the system and everything in the car while it is running. The batteries are only there for when you have more system then you have alternator and drop below its maximum charging ability during heavy use. That or if you are playing the system with the car OFF (like at the beach or something like that.)
basically while the car is running, the alternator should be doing ALL the work.
That being said, if I were to run 2k rms which would pull like what.. 200 give or take amps? If I had a 270xp alt, that would be plenty to run everything with a single batt yeah?
You seem to be forgetting just like everyone else seems to that the car has to be powered b4 the system or anything else.